The present invention relates to curable film-forming compositions containing polyols cured with aminoplasts and carbamoyl triazines.
Of increasing concern in many geographic areas is the encounter with acidic precipitation. Coatings, particularly automotive original equipment coatings that are resistant to such environmental conditions like those that are resistant to etching by atmospheric acid precipitation ("acid etch resistance") are becoming increasingly desirable. Original equipment manufacturers are requiring that coating systems demonstrate acid etch resistance.
In addition to the requirement of acid etch resistance, original equipment coatings must also demonstrate mar and abrasion resistance; i.e., the appearance of the coating must not be detrimentally affected when the coating is contacted with an abrasive material. Mar and abrasion resistance is a desirable property particularly due to the popularity of commercial car washes where brushes are often used to wash car bodies.
A number of commercial coating compositions which demonstrate acid etch resistance do not provide adequate mar and abrasion resistance. Microparticulate materials such as silica, metal sulfides, and crosslinked styrene-butadiene have been added to coating systems to improve mar resistance, but gloss and distinctness of image of the systems is adversely affected due to light scattering at the particle surfaces.
Recently, triisocyanato or tricarbamoyl triazines have been developed as crosslinking agents for coating compositions containing active hydrogen-containing materials. These coating compositions also exhibit acid etch resistance, but mar resistance may be inadequate. The triazine compounds are disclosed in U.S. Pat. Nos. 4,939,213 and 5,084,541. However, these references do not disclose the use of triazines in combination with aminoplasts as crosslinking agents to improve both mar and acid etch resistance of a cured coating.
U.S. Pat. No. 5,574,103 discloses coating compositions comprising polyols, aminoplasts, and carbamoyl triazine compounds. However, the reference does not disclose improved mar and acid etch resistance of cured coatings, nor does it disclose amounts of aminoplast to triazine in the coating composition necessary to improve both mar and acid etch resistance.
It would be desirable to provide a curable composition for use as a coating which avoids the marring problems of the prior art coating systems, while exhibiting excellent acid etch resistance and appearance properties.